title: Acceleration of 7-[methoxy-14C]coumarin-derived carbon dioxide exhalation by cobalt pretreatment in mice.
abstract: Pretreatment of rats with cobaltous chloride has been shown previously to reduce the content of cytochrome P-450 in the hepatic microsomal protein. This is accompanied by a corresponding decrease in substrate oxidation, e.g. ethyl morphine demethylation, in vitro. The present paper shows that pretreatment of C57BL/6J Han mice with 40 mg of CoCl2/kg/day for 2 days results in a decrease of cytochrome P-450 to 60% of its original value. This is accompanied by a corresponding decrease in overall rate of [14C]methacetin demethylation as measured by 14CO2 exhalation. However, when 7-[methoxy-14C]coumarin is the substrate, cobalt-pretreated animals exhale twice as much 14CO2 than normal animals. Considering the decrease in cytochrome P-450 (and assuming linear relationship between metabolic activity and cytochrome P-450 content), this observation suggested a 2.5-fold increase in the specific activity of the remaining cytochrome P-450. This was found to be true in vitro. It is concluded that cobalt pretreatment of mice leads to an enhanced in vivo demethylation rate of 7-[methoxy-14C]coumarin which is explained by a considerably higher molecular monooxygenase activity toward this substrate that is found in vitro.
mesh_terms: D000818:Animals; D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism*; D003035:Cobalt / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003640:Dealkylation; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008861:Microsomes / Q000378:metabolism; D013997:Time Factors; D014468:Umbelliferones / Q000378:metabolism*
chemical_list: D014468:Umbelliferones; D002245:Carbon Dioxide; D003035:Cobalt; C007929:herniarin; D003577:Cytochrome P-450 Enzyme System